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426

of coco-nut oil. Ordinary and absolute iodine numbers exceeding the limiting
values yet observed show the presence of vegetable oils.

Its specific rotation should be very low and negative (about — o-c6°) ; if
it is positive, the presence of Hydnocarpus oil (poisonous), which has the specific
rotation about 55°, is assumed.

It should not contain arachidic and lignoceric acids.

It should not give any colour reaction for seed oils. It must, however, be
borne in mind that a slight coloration may be given by lard from hogs fed with
cottonseed, sesame or other seed cake. In such cases, addition of seed oil to
the lard is proved only when the presence of phytosterol is certain. This is
the case when the acetyl-compound of the sterols obtained as described above
has a corrected melting point higher than 115°.

Lard which gives the colour reactions but does not contain phytosterol
cannot be regarded as containing vegetable oil.

The melting point difference, determined by Bomer's method, should be
such that the value of M.G. -f- 2^ is 71 or more ; if this value is less than 71,
the lard is considered adulterated with tallow, pressed tallow or hardened oil.

In general, the following conclusions, based on the melting point difference
and the phytosterol test, may be drawn 1:

I.  The melting point difference is normal :   the lard is either pure or adul-
terated with vegetable oils.    The phytosterol test  (m.pt.  of the acetyl-com-
pound of the sterols) will demonstrate the presence or absence of vegetable oil.

II.  The melting point difference is below the normal (M.G. -j- zd less than
71) :   the following cases present themselves :—

1.  Phytosterol test negative :   lard contains tallow, hardened animal oils
or both.

2.  Phytosterol test positive :   there may be—

(a)  Addition of vegetable oils or hardened oils ;

(b)         ,,        of tallow (or pressed tallow) and vegetable oils or fats ;

(c)        ,,              ,,            „           ,,              ,,   hardened vegetable oils.

BONE   FAT

This is obtained by de-fatting bones by means of water, steam or solvent
(benzine, carbon disulphide). It varies in consistency but is usually soft
and granular, and it has a yellowish or brown colour and a repulsive odour.
It is somewhat soluble in alcohol, especially when it contains much free
acid. The physical and chemical characters vary somewhat according as
the fat is pure or has been extracted with solvents or steam ; they are given
in Table XLVII.

Bone fat contains cholesterol and, in accordance with the method of
extraction, it may contain various impurities, such as water, lime soaps,
gelatinous substances and hydrocarbons.

The analysis of bone fat for the purpose of determining its commercial
value, includes the following :

' 1. Determination of the Water.—As indicated in the general methods,
or more accurately by heating about 10 grams of the fat at 120° in a current
of hydrogen to constant weight.

2. Determination of Extraneous Impurities  (soaps, mucilaginous
and gelatinous substances, etc.).—50 grams of the fat are well shaken
with a quantity of ether sufficient to dissolve the fatty matter in the cold,
1 Bomer:  Zeitschr. Nahr. Genussmittel, 1914, XXVII, p. 158.itz (Zeit&chr.  Unt. Nahr. Genussmittel, 1913, XXVI, pp. 433, 614, and 1914,